JP6878998B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device that heat-fixes a developer image transferred to a recording medium.

Conventionally, in a fixing device using an endless belt, there is a fixing device provided with two pressure members in the endless belt. For example, Patent Document 1 discloses a configuration in which two pressure members, a pressure pad and a pressure roller, are provided in an endless belt, and the endless belt is sandwiched between these pressure members and a fixing roller. ..

In this technique, when heat-fixing plain paper or the like, a wide nip portion is formed between the two pressurizing members and the fixing roller by pressing the fixing rollers toward the two pressurizing members. To. When a special recording medium is heat-fixed, the fixing roller is retracted from the pressure roller and the pressure pad is pressed toward the fixing roller to narrow the width between the pressure pad and the fixing roller. Nip portion is formed. By heat-fixing the nip portion with such a narrow width, it is possible to suppress the occurrence of wrinkles on a special recording medium.

Japanese Unexamined Patent Publication No. 2014-26295

However, in the technique of Patent Document 1, when a special recording medium is heat-fixed, wrinkles can be suppressed by narrowing the nip width, but plain paper or the like is heat-fixed. Compared to the case where the nip pressure is peaked, only one peak can be created. Therefore, in the technique of Patent Document 1, the peelability of the recording medium from the endless belt is lowered, and there is a possibility that paper jams, that is, jams are likely to occur.

Therefore, an object of the present invention is to suppress deterioration of the peelability of the recording medium from the endless belt.

In order to solve the above problems, in the fixing device according to the present invention, the first endless belt is in contact with the rotating endless belt, the opposing member, and the inner peripheral surface of the endless belt, and the endless belt is sandwiched between the opposing members. A second pressure member that comes into contact with the inner peripheral surface of the endless belt and sandwiches the endless belt between the pressure member, the first pressure member, and the second pressure member are supported. In the moving direction of the portion of the endless belt that is located between the first pressurizing member and the second pressurizing member, the first pressurizing member is placed at the first position and the first pressurizing member. The first pressurizing member and the second pressurizing member are formed by urging one of the frame and the opposing member toward the other, and a moving mechanism for moving between the second position and the second position different from the one position. It is provided with an urging mechanism for generating a holding force for sandwiching the endless belt between the member and the facing member.
In the fixing device, the first pressurizing member, the second pressurizing member, and the first pressurizing member both when the first pressurizing member is located at the first position and when the first pressurizing member is located at the second position. A holding force is generated by the urging mechanism between the facing member and the member.

According to this configuration, by moving the first pressurizing member to the first position or the second position by the moving mechanism, the width of the nip portion between the first pressurizing member and the second pressurizing member and the facing member. Can be changed. Further, since a holding force is generated between the facing member and each pressure member both when the first pressure member is located at the first position and when the first pressure member is located at the second position, the nip portion of the nip portion. Two peaks of nip pressure can be created regardless of the width. Thereby, for example, even when the width of the nip portion is changed according to the type of the recording medium, it is possible to suppress the deterioration of the peelability of the recording medium from the endless belt.

According to the present invention, it is possible to suppress deterioration of the peelability of the recording medium from the endless belt.

It is a figure which shows the schematic structure of the laser printer provided with the fixing device which concerns on 1st Embodiment of this invention. It is sectional drawing which saw from the right of the fixing device when the nip width is a 1st width. It is sectional drawing which saw from the right of the fixing device when the nip width is a 2nd width. It is a perspective view which shows each member of a fixing device by disassembling. It is sectional drawing which saw from the top the cross section of the fixing device cut by the plane orthogonal to the vertical direction. It is sectional drawing which shows the structure around stay, it is the sectional drawing (a) of I-I of FIG. 5, the sectional view (b) of II-II of FIG. 5, and the sectional view (c) of III-III of FIG. .. It is a figure (a), (b) which shows the operation of a oscillating gear and a cam. It is sectional drawing which saw the fixing apparatus which concerns on 2nd Embodiment from the right, and is the figure which shows the state when the nip width is a 1st width. It is sectional drawing which saw the fixing apparatus which concerns on 2nd Embodiment from the right, and is the figure which shows the state when the nip width is 2nd width. It is a figure which shows the connecting part of a pressure arm and a bearing. It is sectional drawing which looked at the cross section of the structure around a pressure roller cut by the plane orthogonal to the vertical direction from the top. It is sectional drawing which saw the fixing apparatus which concerns on 3rd Embodiment from the right, and is the figure which shows the state when the nip width is 1st width. It is sectional drawing which saw the fixing apparatus which concerns on 3rd Embodiment from the right, and is the figure which shows the state when the nip width is 2nd width.

[First Embodiment]
Next, the first embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, a schematic configuration of the laser printer 1 provided with the fixing device 100 of the present invention will be described, and then the feature portions of the present invention will be described in detail.

Further, in the following description, the direction will be described in the direction shown in FIG. That is, the left side in FIG. 1 is "front", the right side is "rear", the front side is "right", and the back side is "left". Further, the vertical direction in FIG. 1 is defined as "up and down".

As shown in FIG. 1, the laser printer 1 includes a paper feeding unit 3 for supplying paper S, an exposure device 4, a process cartridge 5 for transferring a toner image onto the paper S, and paper in the main body housing 2. It mainly includes a fixing device 100 that heat-fixes the toner image on S.

The paper feed unit 3 is provided in the lower part of the main body housing 2, and includes a paper feed tray 31 and a paper feed mechanism 33. The paper S housed in the paper feed tray 31 is supplied toward the process cartridge 5 by the paper feed mechanism 33.

The exposure apparatus 4 is arranged in the upper part of the main body housing 2 and includes a laser emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, etc., which are indicated by omitting reference numerals. In this exposure apparatus 4, the laser beam (see chain line) based on the image data emitted from the laser emitting unit is scanned at high speed on the surface of the photoconductor drum 61 to expose the surface of the photoconductor drum 61.

The process cartridge 5 is arranged below the exposure apparatus 4, and is removable from the main body housing 2 through an opening formed when the front cover 21 provided in the main body housing 2 is opened. The process cartridge 5 is composed of a drum unit 6 and a developing unit 7.

The drum unit 6 mainly includes a photoconductor drum 61, a charger 62, and a transfer roller 63. Further, the developing unit 7 is detachable from the drum unit 6, and mainly includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner accommodating portion 74 for accommodating toner. There is.

In this process cartridge 5, the surface of the photoconductor drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser beam from the exposure apparatus 4, so that an image is displayed on the photoconductor drum 61. An electrostatic latent image based on the data is formed. Further, the toner in the toner accommodating portion 74 is supplied to the developing roller 71 via the supply roller 72, enters between the developing roller 71 and the layer thickness regulating blade 73, and forms a thin layer having a constant thickness on the developing roller 71. It is carried on.

The toner supported on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photoconductor drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photoconductor drum 61. After that, the paper S is conveyed between the photoconductor drum 61 and the transfer roller 63, so that the toner image on the photoconductor drum 61 is transferred onto the paper S.

The fixing device 100 is provided behind the process cartridge 5. When the paper S on which the toner image is transferred passes through the fixing device 100, the toner image is heat-fixed on the paper S. The paper S on which the toner image is heat-fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

As shown in FIG. 2, the fixing device 100 includes a heating roller 110 as an example of an opposing member, a pressure unit 200, a fixing frame 120, a pressure arm 130 as an example of a frame, and an example of an urging mechanism. The tension coil spring 140 and the like are provided. The fixing frame 120 is made of, for example, resin.

The heating roller 110 is a roller that rotates about a rotation axis along the left-right direction. The heating roller 110 includes a cylindrical base tube 111 made of metal and an elastic layer 112 provided on the outer peripheral surface of the base tube 111. The elastic layer 112 is made of an elastically deformable material such as silicone rubber. The raw tube 111 is rotatably supported by the fixing frame 120. A heater 113 is provided inside the raw tube 111.

The pressure arm 130 is a plate-shaped member made of metal or the like, and one end thereof is rotatably supported by the fixing frame 120. One pressure arm 130 is provided on each of the left and right sides of the pressure unit 200, and supports each end of the pressure unit 200 in the left-right direction.

The tension coil spring 140 is a spring that generates a nip pressure between the heating roller 110 and the pressurizing unit 200 by urging the pressurizing arm 130 upward, specifically toward the heating roller 110. The tension coil spring 140 is connected to the other end of the pressure arm 130 opposite to the rotation shaft and the fixing frame 120.

Although not shown, the fixing device 100 provides a switching mechanism for switching the pressurizing arm 130 from the pressing position shown in FIG. 2 to a retracting position (not shown) that is farther from the heating roller 110 than the pressing position. I have. When the pressurizing arm 130 is located at the pressing position, a predetermined nip pressure is generated between the heating roller 110 and the pressurizing unit 200, and when the pressurizing arm 130 is located at the retracting position, the pressurizing roller 110 and the pressurizing unit 200 are pressurized. The nip pressure between the unit 200 and the unit 200 is weaker than the predetermined nip pressure, for example, 0.

The pressurizing unit 200 is arranged below the heating roller 110. The pressure unit 200 includes an endless belt 210, a pressure pad 220 as an example of a first pressure member, a pressure roller 230 as an example of a second pressure member, a moving mechanism 240, and a sliding contact member. As an example, a movable guide 250 and a displacement mechanism 260 are provided.

The endless belt 210 is a belt having heat resistance and flexibility that is heated by the heating roller 110. The endless belt 210 is driven to rotate by rotating the heating roller 110 in a state of frictional engagement with the heating roller 110. Specifically, the endless belt 210 rotates clockwise in FIG. The endless belt 210 is arranged so that its width direction is along the left-right direction. The width of the endless belt 210, that is, the length in the left-right direction is larger than the length in the left-right direction of the pressure pad 220, and is larger than the length in the left-right direction of the roller body 231 described later of the pressure roller 230.

A predetermined portion 211 of the endless belt 210 located between the pressure pad 220 and the pressure roller 230 moves substantially in the front-rear direction. That is, in the present embodiment, the moving direction of the predetermined portion 211 corresponds to the front-back direction.

The pressure pad 220 can move in the front-rear direction with respect to the pressure arm 130 at a position on the front side of the pressure roller 230, that is, on the upstream side in the movement direction described above. The pressure pad 220 includes a pad body 221 made of an elastically deformable material such as silicone rubber, and a holder 222 that supports the pad body 221.

The pad body 221 is in contact with the inner peripheral surface of the endless belt 210, and sandwiches the endless belt 210 with the heating roller 110. The pad body 221 is formed in a rectangular parallelepiped shape that is long in the left-right direction. The pad body 221 is configured to be softer than the elastic layer 112 of the heating roller 110, that is, to be easily elastically deformed. The pad body 221 is fixed to the upper surface of the holder 222.

The holder 222 is formed in a rectangular parallelepiped shape that is long in the left-right direction. The holder 222 is larger than the pad body 221 in the vertical direction. The lower surface of the holder 222 is located below the pressure roller 230 in the vertical direction. The holder 222 is supported by the pressure arm 130 via a stay 241 described later. As a result, the pressure pad 220 is pressed against the heating roller 110 by the pressure arm 130, and a holding force for sandwiching the endless belt 210 between the pressure pad 220 and the heating roller 110 is generated.

The lower surface of the holder 222 can be slidably moved in the front-rear direction on the lower wall 241A described later of the stay 241. As a result, the pressure pad 220 can move in the front-rear direction between the first position shown in FIG. 2 and the second position shown in FIG. 3, which is different from the first position.

In the present embodiment, when the pressure pad 220 is located at the first position, the distance between the pressure pad 220 and the pressure roller 230 is the first distance, and the pressure pad 220 is located at the second position. Sometimes, the distance between the pressure pad 220 and the pressure roller 230 is a second distance smaller than the first distance. That is, the second position is closer to the pressure roller 230 than the first position. Then, both when the pressure pad 220 is located at the first position and when it is located at the second position, a holding force by the tension coil spring 140 is generated between the pressure pad 220 and the heating roller 110. , Each position is set. As a result, when the pressure pad 220 is located at the first position, the width of the nip portion in the front-rear direction, which is the contact portion between the endless belt 210 and the heating roller 110, becomes the first width N1, and the pressure pad 220 becomes the first. When located at the two positions, the width of the nip portion in the front-rear direction is the second width N2, which is smaller than the first width N1.

The pressure roller 230 is a roller that rotates about a rotation axis along the left-right direction. The pressure roller 230 is in contact with the inner peripheral surface of the endless belt 210, and sandwiches the endless belt 210 with the heating roller 110. The pressurizing roller 230 includes a roller body 231 having a cylindrical outer peripheral surface, and a rotating shaft 232 protruding from each end surface of the roller body 231 in the left-right direction.

The roller body 231 is made of an elastically deformable material such as silicone rubber. The roller body 231 is configured to be harder than the elastic layer 112 of the heating roller 110, that is, to be less likely to be elastically deformed. Although it is shown in FIG. 2 that neither the elastic layer 112 of the heating roller 110 nor the roller body 231 is deformed, in reality, the elastic layer 112 of the heating roller 110 is the peripheral surface of the roller body 231. It is deformed along.

The rotary shaft 232 is rotatably supported by a bearing 233 fixed to the pressurizing arm 130. That is, the pressure roller 230 is supported by the pressure arm 130 via the bearing 233. As a result, the pressure roller 230 is pressed against the heating roller 110 by the pressure arm 130, and a holding force for sandwiching the endless belt 210 between the pressure roller 230 and the heating roller 110 is generated. In this embodiment, the pressure roller 230 and the bearing 233 correspond to the second pressure member.

Then, the rotary shaft 232 is supported by the bearing 233 fixed to the pressure arm 130, so that the position of the pressure roller 230 is fixed with respect to the pressure arm 130 in the front-rear and up-down directions. In other words, the position of the pressure roller 230 is fixed with respect to the pressure arm 130 in a direction orthogonal to the width direction of the endless belt 210. As a result, the pressure roller 230 is always pressed toward the heating roller 110 regardless of the position of the pressure pad 220. Therefore, a holding force by the tension coil spring 140 is generated between the pressure roller 230 and the heating roller 110 both when the pressure pad 220 is located at the first position and when the pressure pad 220 is located at the second position. ing.

The moving mechanism 240 is a mechanism for moving the pressure pad 220 between the first position shown in FIG. 2 and the second position shown in FIG. 3 in the front-rear direction. The moving mechanism 240 mainly includes a stay 241, a compression coil spring 242 as an example of the first urging member, a cam 243, and a swing gear G1, a drive gear G2, and a rotation shaft 243A shown in FIG. ing.

As shown in FIG. 4, the stay 241 is a member long in the left-right direction, and each end portion in the left-right direction is fixed to each pressure arm 130. The stay 241 has a lower wall 241A, a front wall 241B extending upward from the front end of the lower wall 241A, and a rear wall 241C extending upward from the rear end of the lower wall 241A. The lower wall 241A supports the pressure pad 220 from below (see FIG. 6A).

Holes A1 penetrating in the vertical direction are formed at each end of the lower wall 241A in the horizontal direction. The hole A1 is a hole for passing the protruding portion 254 of the movable guide 250, which will be described later, and is arranged at the same position as the cam main body 243B and the protruding portion 254 of the movable guide 250 in the left-right direction (FIGS. 5 and 6 (FIGS. 5 and 6). c) See). A convex portion A2 protruding toward the pressure arm 130 is formed at the rear end portion of the lower wall 241A at each end surface in the left-right direction.

The front wall 241B projects upward from the rear wall 241C. A convex portion B2 protruding toward the pressurizing arm 130 is formed on the upper portion of the front wall 241B at each end surface in the left-right direction. As shown in FIG. 2, a fixing guide 270 that guides the inner peripheral surface of the endless belt 210 is fixed to the front surface of the front wall 241B. The outer surface of the fixed guide 270 in contact with the endless belt 210 is formed in a substantially arc shape in cross section.

As shown in FIG. 4, the rear wall 241C is formed from the tip of the convex portion A2 on the left side of the lower wall 241A to the tip of the convex portion A2 on the right side. The pressure arm 130 has a first support hole 131 for supporting the convex portion B2 of the stay 241 and an L-shaped second support for supporting the convex portion A2 of the stay 241 and the left-right end of the rear wall 241C. Hole 132 is formed. The position of the stay 241 supported by the support holes 131 and 132 of the pressure arm 130 with respect to the pressure arm 130 is fixed.

As shown in FIG. 5, the compression coil spring 242 is a spring that urges the pressure pad 220 from the first position to the second position. In the present embodiment, the compression coil spring 242 urges the pressure pad 220 toward the pressure roller 230. The compression coil spring 242 is arranged between the cam body 243B and the pressure pad 220, which will be described later, in the left-right direction. Further, the front end portion of the compression coil spring 242 is fixed to the rear surface of the front wall 241B of the stay 241. At the rear end of the compression coil spring 242, a contact member 244 that abuts on the rotation shaft 243A of the cam 243 is provided. As shown in FIG. 6B, the contact member 244 has a substantially semi-cylindrical recess 244A along the outer peripheral surface of the rotation shaft 243A of the cam 243.

As shown in FIG. 4, the cam 243 has a rotating shaft 243A and a cam main body 243B that rotates together with the rotating shaft 243A. The rotation shaft 243A is provided along the width direction of the endless belt 210, and is arranged so as to penetrate the holder 222 in the left-right direction. Specifically, the holder 222 is formed with an elongated hole 222A penetrating in the left-right direction, and the rotation shaft 243A is arranged so as to penetrate the elongated hole 222A. That is, the cam 243 is provided on the pressure pad 220 by inserting and engaging the rotation shaft 243A through the elongated hole 222A. The length of the elongated hole 222A is larger than the outer diameter of the rotating shaft 243A in the direction in which the holding force is generated between the pressure pad 220 and the heating roller 110, that is, in the vertical direction.

The elongated hole 222A is a hole that is elongated in the vertical direction. The rotation shaft 243A is movable in the vertical direction with respect to the holder 222. The vertical length of the elongated hole 222A is larger than the vertical movement amount of the pressurizing arm 130 (the movement amount from the pressing position to the retracting position described above). Further, the lower end of the elongated hole 222A is located below the rotation shaft 243A of the cam 243 when the pressurizing arm 130 is located at the pressing position (see FIG. 6A).

One cam body 243B is provided on each side of the holder 222 in the left-right direction. The cam main body 243B is formed so as to protrude outward in the radial direction of the rotation shaft 243A from the rotation shaft 243A, and can rotate together with the rotation shaft 243A. The tip surface of the cam body 243B farthest from the rotation shaft 243A faces rearward and contacts the bearing 233 when the pressure pad 220 is in the first position shown in FIG. That is, the pressure pad 220 is located at the first position when the tip surface of the cam body 243B comes into contact with the bearing 233.

Further, the tip surface of the cam body 243B is separated from the bearing 233 when the pressure pad 220 is in the second position shown in FIG. That is, the pressure pad 220 is located at the second position because the tip surface of the cam body 243B is separated from the bearing 233. Further, when the pressure pad 220 is in the second position shown in FIG. 3, the tip surface of the cam body 243B faces downward and comes into contact with the protruding portion 254 of the movable guide 250 described later.

The end of the rotating shaft 243A is supported by an arcuate bearing 121 provided in the fixing frame 120 through an insertion hole 133 formed in the pressure arm 130. The bearing 121 has an arc hole 121A that supports the bearing 121 while penetrating the rotating shaft 243A. As a result, the rotation shaft 243A can move in the substantially front-rear direction along the arc hole 121A.

The insertion hole 133 is a hole through which the rotation shaft 243A is inserted, and its length in the front-rear direction is larger than the outer diameter of the rotation shaft 243A. Specifically, the length of the insertion hole 133 in the front-rear direction is larger than the amount of movement of the rotation shaft 243A in the front-rear direction, and the length of the insertion hole 133 in the vertical direction is larger than the amount of movement of the pressurizing arm 130 in the vertical direction. Is also big. As a result, the pressure arm 130 is prevented from interfering with the rotating shaft 243A.

The end portion of the rotating shaft 243A protrudes outward in the left-right direction from the fixing frame 120. A swing gear G1 is fixed to the end of the rotation shaft 243A.

As shown in FIG. 7A, the swing gear G1 is a gear that meshes with the drive gear G2 rotatably supported by the fixing frame 120 and moves around the drive gear G2, in detail, swings. .. In order to move the swing gear G1 around the drive gear G2, a known swing is provided, such as providing an arm member for connecting the rotation shaft of the drive gear G2 and the rotation shaft 243A of the swing gear G1. The structure of the gear mechanism may be adopted. The rotation shaft 243A is located at the front end of the arc hole 121A when the pressure pad 220 is located at the first position shown in FIG. At this time, the tip of the cam body 243B faces rearward.

When a rotational driving force in a predetermined direction is transmitted to the drive gear G2 from a drive source (not shown), the drive gear G2 rotates counterclockwise as shown in FIG. 7B, and the swing gear G1 moves. While rotating clockwise, it moves around the drive gear G2 counterclockwise as shown. At this time, the rotation shaft 243A also moves from the front end portion to the rear end portion of the arc hole 121A while rotating clockwise in the figure. Since the rearward movement of the rotation shaft 243A is assisted by the urging force of the compression coil spring 242 (see FIG. 2), the rotation shaft 243A smoothly moves rearward. When the rotation shaft 243A rotates, the cam body 243B also rotates clockwise, and the direction of the tip is switched from the rear to the lower side.

When a rotational driving force in a direction opposite to a predetermined direction is transmitted to the drive gear G2 from a drive source (not shown), the drive gear G2 rotates clockwise as shown in FIG. 7A and swings. While the gear G1 rotates counterclockwise, it moves around the drive gear G2 in the clockwise direction shown in the figure. At this time, the rotation shaft 243A also moves from the rear end portion to the front end portion of the arc hole 121A while rotating counterclockwise as shown in the drawing. When the rotation shaft 243A rotates, the cam body 243B also rotates counterclockwise, and the direction of the tip is switched from the lower side to the rear side. In the process of switching the direction of the tip of the cam body 243B from the bottom to the rear, the pressure pad 220 causes the compression coil spring 242 (see FIG. 2) due to the reaction of the force that the tip of the cam body 243B pushes the bearing 233 (see FIG. 2). It moves from the second position to the first position against the urging force.

By such movement of the rotation shaft 243A in the front-rear direction, the pressure pad 220 that engages with the rotation shaft 243A can also be moved in the front-rear direction, so that the pressure pad 220 can be moved to the first position and the second position. Can be positioned appropriately. When the rotating shaft 243A engages with the vertically long elongated hole 222A formed in the pressure pad 220, the vertical movement of the rotating shaft 243A that moves along the arc hole 121A is the elongated hole 222A. Since it can be absorbed by the pressure pad 220, it is possible to suppress the pressure pad 220 from moving up and down.

As shown in FIG. 2, the movable guide 250 is a member that guides the inner peripheral surface of the endless belt 210, and is farther from the third position shown in FIG. 2 and the rotation center of the cam 243 than the third position. It is possible to move vertically between the position and the fourth position (position in FIG. 3). As shown in FIG. 4, the movable guide 250 has a guide surface 251 having a substantially arcuate cross-sectional view that contacts the inner peripheral surface of the endless belt 210, an upper surface 252, and an end surface 253. The upper surface 252 is located on the side opposite to the guide surface 251 in the vertical direction. The upper surface 252 is orthogonal to the vertical direction. As shown in FIG. 2, the upper surface 252 comes into contact with the lower wall 241A of the stay 241 when the movable guide 250 is in the third position, and the lower wall of the stay 241 when the movable guide 250 is in the fourth position. Leave 241A.

At each end of the movable guide 250 in the left-right direction, a protruding portion 254 protruding upward from the upper surface 252 is formed. The protruding portion 254 is formed in a substantially arc shape in a cross-sectional view that is convex upward. When the movable guide 250 is located at the third position, the projecting portion 254 projects upward from the lower wall 241A through the hole A1 formed in the lower wall 241A of the stay 241.

The end surface 253 is a surface orthogonal to the left-right direction, and connects the upper surface 252 and each end portion of the guide surface 251 in the left-right direction. Two protrusions 255 are formed on the end face 253 so as to project toward the pressure arm 130. The protrusions 255 are arranged at intervals in the front-rear direction.

The pressurizing arm 130 is formed with two elongated holes 134 that support each protrusion 255 so as to be movable in the vertical direction. As a result, the movable guide 250 can move in the vertical direction with respect to the pressure arm 130.

The displacement mechanism 260 is a mechanism that displaces the position of the movable guide 250 in conjunction with the operation of the moving mechanism 240. Specifically, the displacement mechanism 260 moves the movable guide 250 to the third position when the pressure pad 220 moves from the first position (position in FIG. 2) to the second position (position in FIG. 3) by the operation of the moving mechanism 240. It is configured to move from the position (position in FIG. 2) to the fourth position (position in FIG. 3). Further, the displacement mechanism 260 is configured to move the movable guide 250 from the fourth position to the third position when the pressure pad 220 moves from the second position to the first position by the operation of the moving mechanism 240. There is.

Specifically, the displacement mechanism 260 urges the cam 243, the protrusions 255 of the movable guide 250, the elongated holes 134 of the pressure arm 130, and the movable guide 250 from the fourth position to the third position. It includes a tension coil spring (not shown). When the pressure pad 220 is in the second position, the cam 243 contacts the protrusion 254 of the movable guide 250 and holds the movable guide 250 in the fourth position (see FIG. 3). Further, the cam 243 is separated from the movable guide 250 when the pressure pad 220 is located at the first position (see FIG. 2).

Next, the operation of each member of the fixing device 100 will be described. First, the operation of each member when the pressure pad 220 is moved from the first position to the second position will be described.

When moving the pressure pad 220 in the front-rear direction, first, the pressure arm 130 is switched from the pressing position to the retracting position. As a result, the nip pressure between the heating roller 110 and the pressure pad 220 is released, and the pressure pad 220 can be easily moved. In the following description, the movement of the pressure pad 220 will be described with reference to FIGS. 2 and 3, but the heating roller 110 is in a state of being separated from the pressure unit 200.

As shown in FIG. 2, in a state where the pressurizing pad 220 from which the nip pressure is released is located at the first position, when a rotational driving force in a predetermined direction is input to the drive gear G2 shown in FIG. 7A, it swings. The gear G1 moves while rotating to the position shown in FIG. 7B. As a result, the rotation shaft 243A of the cam 243 moves rearward along the arc hole 121A, and the direction of the tip surface of the cam body 243B is switched from the rear to the lower side.

When the cam body 243B rotates in this way, the tip surface of the cam body 243B comes off from the bearing 233 as shown in FIG. Therefore, the pressure pad 220 is pushed backward by the rotating shaft 243A that receives the force from the drive gear G2 and the urging force of the compression coil spring 242, and moves from the first position to the second position. At this time, the movable guide 250 is pushed downward by the cam main body 243B and moves from the third position to the fourth position.

After that, the pressure arm 130 is switched from the retracted position to the pressed position. As a result, a holding force for sandwiching the endless belt 210 between the heating roller 110, the pressure pad 220, and the pressure roller 230 is generated, so that the width of the nip portion is from the first width N1 to the first width N1. Also switches to a small second width N2.

Further, at this time, since the distance between the pressure pad 220 and the pressure roller 230 is reduced, the amount of the heating roller 110 that enters between them is reduced, and the endless belt 210 may be loosened. On the other hand, in the present embodiment, since the movable guide 250 is located at the fourth position outside the third position, an appropriate tension can be applied to the endless belt 210.

As shown in FIG. 3, in a state where the pressure pad 220 from which the nip pressure is released is located at the second position, a rotational driving force in a direction opposite to a predetermined direction is input to the drive gear G2 shown in FIG. 7 (b). Then, the swing gear G1 moves while rotating to the position shown in FIG. 7A. As a result, the rotation shaft 243A of the cam 243 moves forward along the arc hole 121A, and the direction of the tip surface of the cam main body 243B is switched from the lower side to the rear side.

When the cam body 243B rotates in this way, the tip surface of the cam body 243B presses the bearing 233 as shown in FIG. Therefore, the pressure pad 220 is pushed forward by the rotating shaft 243A that receives the reaction force of the force from the drive gear G2 and the force that the cam body 243B presses the bearing 233, and moves from the second position to the first position. Moving. Further, at this time, since the cam main body 243B is disengaged from the movable guide 250, the movable guide 250 moves from the fourth position to the third position by the urging force of the spring (not shown).

After that, the pressure arm 130 is switched from the retracted position to the pressed position. As a result, a holding force for sandwiching the endless belt 210 between the pressure pad 220, the pressure roller 230, and the heating roller 110 is generated, so that the width of the nip portion is changed from the second width N2 to the second width N2. Also switches to a large first width N1.

Further, at this time, since the distance between the pressure pad 220 and the pressure roller 230 becomes large, the amount of the heating roller 110 entering between them increases, and a large load may be applied to the endless belt 210. On the other hand, in the present embodiment, since the movable guide 250 is located at the third position inside the fourth position, it is possible to suppress a large load from being applied to the endless belt 210.

Based on the above, the following effects can be obtained in the present embodiment.
By moving the pressure pad 220 to the first position or the second position by the moving mechanism 240, the width of the nip portion between the pressure unit 200 and the heating roller 110 can be changed. Further, a holding force is generated between the heating roller 110 and the pressure pad 220 and the pressure roller 230 both when the pressure pad 220 is located at the first position and when the pressure pad 220 is located at the second position. Therefore, regardless of the width of the nip portion, two peaks of the nip pressure can be created. Thereby, for example, even when the width of the nip portion is changed according to the type of the paper S, it is possible to suppress the deterioration of the peelability of the paper S from the endless belt 210.

Of the two pressure members (pressure pad 220, pressure roller 230), the position of the pressure member on the downstream side in the moving direction of the predetermined portion 211 of the endless belt 210 is fixed with respect to the pressure arm 130. , The nip width can be changed without moving the pressure member on the downstream side in the moving direction. Therefore, the peelability of the paper S can be further improved.

Since the cam body 243B comes into contact with the non-rotating bearing 233, wear of the cam body 243B can be suppressed.

Since the displacement mechanism 260 that displaces the position of the movable guide 250 in conjunction with the operation of the moving mechanism 240 is provided, the tension of the endless belt 210 can be stabilized regardless of the change in the nip width.

Since the movable guide 250 is moved by using the cam 243 for moving the pressure pad 220, for example, as compared with the configuration in which the movable guide is moved by a cam different from the cam that moves the pressure pad. The number of parts can be reduced.

[Second Embodiment]
Next, the second embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Since this embodiment is a modification of the structure of a part of the fixing device 100 according to the first embodiment described above, the same reference numerals are given to the components substantially the same as those of the first embodiment. However, the description thereof will be omitted.

As shown in FIGS. 8 and 9, in the fixing device 300 according to the second embodiment, the pressure pad 220 is fixed to the pressure arm 130, and the pressure roller 230 moves in the front-rear direction with respect to the pressure arm 130. It differs from the first embodiment in that it can be moved. That is, in the second embodiment, the pressure roller 230 corresponds to the first pressure member, and the pressure pad 220 corresponds to the second pressure member.

The pressure pad 220 is fixed to a stay 341 fixed to the pressure arm 130. The pressure pad 220 is provided with a cam 243. The pressure pad 220 rotatably supports the rotation shaft 243A of the cam 243. Specifically, the hole through which the rotation shaft 243A formed in the pressure pad 220 passes is not a long hole 222A as in the first embodiment, but a round hole. As a result, the cam 243 is fixed at a position in the front-rear and up-down directions with respect to the pressure pad 220. Therefore, in the second embodiment, the mechanism provided with the swing gear G1 as in the first embodiment becomes unnecessary, and the structure for driving the cam 243 can be simplified.

The stay 341 is formed in an L shape in cross section. The stay 341 has a slit 341A for passing the cam main body 243B. The movable guide 350 is different from the first embodiment only in that it does not have a protrusion 254, and other structures are substantially the same as those of the first embodiment.

The pressurizing roller 230 is movable in the front-rear direction between the first position shown in FIG. 8 and the second position shown in FIG. Specifically, as shown in FIG. 10, the pressurizing arm 130 has a fitting hole 135 into which the bearing 233 supporting the pressurizing roller 230 is fitted. The fitting hole 135 is an elongated hole that is long in the front-rear direction. That is, the length of the fitting hole 135 in the front-rear direction is larger than the outer diameter of the bearing 233. The bearing 233 is supported by a fitting hole 135 so as to be movable in the front-rear direction.

As shown in FIG. 11, the pressure arm 130 is provided with a compression coil spring 242 as an example of the first urging member. Specifically, the pressurizing arm 130 has a support portion 136 that is arranged rearward from the bearing 233 of the pressurizing roller 230. The compression coil spring 242 is arranged between the bearing 233 and the support portion 136, and urges the pressure roller 230 toward the pressure pad 220.

Then, as shown in FIG. 8, the pressure roller 230 is located at the first position when the tip surface of the cam body 243B comes into contact with the bearing 233. Further, as shown in FIG. 9, the pressure roller 230 is positioned at the second position by the urging force of the compression coil spring 242 by separating the tip surface of the cam body 243B from the bearing 233.

Next, the operation of each member of the fixing device 300 will be described. Since the switching operation of the pressure arm 130 is the same as that of the first embodiment, the description thereof will be omitted.

As shown in FIG. 8, when the pressurizing roller 230 is located at the first position and a rotational driving force is applied to the cam 243 in the clockwise direction, the cam body 243B rotates clockwise in the cam body. The tip surface of 243B comes off the bearing 233. As a result, as shown in FIG. 9, the pressure roller 230 is moved from the first position to the second position by the compression coil spring 242. At this time, the movable guide 350 is pushed downward by the cam main body 243B and moves from the third position to the fourth position.

As shown in FIG. 9, when the pressure roller 230 is located at the second position and the rotational driving force shown in the counterclockwise direction is input to the cam 243, the cam body 243B rotates counterclockwise in the figure. As the tip surface of the cam body 243B retracts from the movable guide 350, the movable guide 350 moves from the fourth position to the third position by a spring (not shown). Further, when the tip portion of the cam body 243B comes into contact with the bearing 233, the cam body 243B presses the bearing 233 rearward against the urging force of the compression coil spring 242. As a result, the pressure roller 230 moves from the second position to the first position.

As described above, according to the second embodiment, the following effects can be obtained.
Since the cam 243 is provided on the pressure pad 220 whose position in the front-rear and up-down directions is fixed, the structure for transmitting the driving force to the cam 243 can be simplified.

Since the cam body 243B comes into contact with the non-rotating bearing 233, wear of the cam body 243B can be suppressed.

[Third Embodiment]
Next, the third embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Since this embodiment is a modification of the structure of a part of the fixing device 100 according to the first embodiment described above, the same reference numerals are given to the components substantially the same as those of the first embodiment. However, the description thereof will be omitted.

As shown in FIG. 12, the fixing device 400 according to the third embodiment is different from the first embodiment in that the movable guide 450 moves mainly by the force applied from the endless belt 210. Specifically, in this embodiment, the stay 441 is different from the first embodiment in that it does not have the hole A1 described above and has a front wall 441B different from that of the first embodiment.

The front wall 441B includes a first wall B11 projecting upward from the front end portion of the lower wall 241A, a second wall B12 projecting forward from the upper end portion of the first wall B11, and upward from the front end portion of the second wall B12. It has a protruding third wall B13. One end of the compression coil spring 242 is fixed to the rear surface of the third wall B13.

The movable guide 450 is supported by the pressure arm 130 so as to be movable in the front-rear direction. The connection structure between the movable guide 450 and the pressure arm 130 may be substantially the same as the connection structure between the movable guide 250 and the pressure arm 130 in the first embodiment.

A guide urging spring 442 as an example of the third urging member is provided between the first wall B11 and the movable guide 450. The guide urging spring 442 urges the movable guide 450 forward, that is, urges the movable guide 450 from the third position to the fourth position. In this embodiment, the displacement mechanism includes a guide urging spring 442, a connecting structure of the movable guide 450 and the pressure arm 130, and does not include a cam 243 for moving the pressure pad 220.

Further, a fixing guide 470 is fixed to the lower surface of the lower wall 241A. The outer surfaces of the movable guide 450 and the fixed guide 470 are formed in a substantially arc shape in cross-sectional view, and are in contact with the inner peripheral surface of the endless belt 210.

Further, the tip surface of the cam body 243B, that is, the contact surface that comes into contact with the bearing 233, has a recess 243C that accommodates a part of the bearing 233. The recess 243C is formed in an arc shape in a cross-sectional view along the outer peripheral surface of the bearing 233.

Next, the operation of each member of the fixing device 400 will be described. Since the switching operation of the pressure arm 130 and the operation of the pressure pad 220 are the same as those in the first embodiment, the description thereof will be omitted.

As shown in the order of FIGS. 12 to 13, when the pressure pad 220 is moved from the first position to the second position and the pressure unit 200 is pressed against the heating roller 110, the pressure pad 220 and the pressure roller 230 are pressed. Since the interval is narrow, the endless belt 210 is in a loosened state. When the endless belt 210 is loosened in this way, the movable guide 450 is moved from the third position to the fourth position by the urging force of the guide urging spring 442, so that an appropriate tension can be applied to the endless belt 210. it can.

Further, as shown in the order of FIGS. 13 to 12, when the pressurizing pad 220 is moved from the second position to the first position and the pressurizing unit 200 is pressed against the heating roller 110, the pressurizing pad 220 and the pressurizing pad 220 are pressurized. Since the distance from the roller 230 is wide, the tension of the endless belt 210 becomes high. When the tension of the endless belt 210 becomes high in this way, the endless belt 210 presses the movable guide 450 against the urging force of the guide urging spring 442, so that the movable guide 450 moves from the fourth position to the third position. Move to position. Thereby, for example, as compared with the structure in which the movable guide 450 is fixed at the fourth position, it is possible to suppress a large load from being applied to the endless belt 210.

As described above, according to the third embodiment, the following effects can be obtained.
Since the tip surface of the cam body 243B has the recess 243C, the pressure pad 220 can be satisfactorily held in the first position.

By providing the guide urging spring 442 that urges the movable guide 450 from the third position to the fourth position, the movable guide 450 can be moved according to the degree of relaxation of the endless belt 210. Further, in this structure, since the cam 243 for moving the pressure pad 220 is not used for moving the movable guide 450, the load applied to the cam 243 can be suppressed.

The present invention is not limited to the above embodiment, and can be used in various forms as illustrated below.

In the above embodiment, the pressure arm 130 has been exemplified as the frame, but the present invention is not limited to this, and the frame may be, for example, a fixing frame. In this case, the heating roller 110 may be urged toward the fixing frame by the urging mechanism.

In the above embodiment, the heating roller 110 has been exemplified as the opposing member, but the present invention is not limited to this. For example, when the heat source is provided in the endless belt, the opposing member may be, for example, a pressure roller. ..

In the above embodiment, only the first pressurizing member is moved, but the present invention is not limited to this, and the nip width is changed by moving both the first pressurizing member and the second pressurizing member. It may be configured as follows.

In the above embodiment, the second position is a position closer to the second pressurizing member than the first position, but the present invention is not limited to this, and the second position is the second pressurizing than the first position. It may be located far from the member. That is, the first urging member may urge the first pressurizing member in a direction away from the second pressurizing member.

In the above embodiment, a cam 243 that rotates as a cam has been illustrated, but the present invention is not limited to this, and for example, the cam may be a linearly moving cam that moves on a straight line.

Each spring shown in the embodiment is not limited to the type as in the embodiment, and may be appropriately changed to other types such as a torsion spring and a leaf spring.

In the above embodiment, a mechanism for movably supporting a member such as a pressure pad 220 or a movable guide 250 is composed of a hole and a protrusion, but the present invention is not limited to this, and for example, the protrusion and the protrusion are moved. It may be composed of a guide rail that supports it as much as possible.

In the structure in which the first pressurizing member is moved by using the swing gear as in the first embodiment, the first urging member and the cam may not be provided. In this case, for example, instead of the movable guide 250 as the sliding contact member, a fixed guide fixed to the stay 241 may be provided at the position where the movable guide 250 is arranged (the position shown in FIG. 2), or the sliding contact member may be provided. A cam for moving the moving mechanism may be provided separately from the moving mechanism.

In addition, each element described in the above-described embodiment and modification may be arbitrarily combined and implemented.

100 Fixing device 110 Heating roller 130 Pressure arm 140 Tension coil spring 210 Endless belt 211 Predetermined part 220 Pressure pad 230 Pressure roller 240 Movement mechanism

Claims (11)

With a rotating endless belt,
Opposing members and
A first pressure member that comes into contact with the inner peripheral surface of the endless belt and sandwiches the endless belt with the opposing member.
A second pressure member that comes into contact with the inner peripheral surface of the endless belt and sandwiches the endless belt with the opposing member.
A frame that supports the first pressurizing member and the second pressurizing member, and
In the moving direction of the portion of the endless belt located between the first pressurizing member and the second pressurizing member, the first pressurizing member is placed at the first position and the first position. A moving mechanism that moves between different second positions,
By urging one of the frame and the opposing member toward the other, a holding force for sandwiching the endless belt between the first pressing member and the second pressing member and the opposing member. Equipped with an urging mechanism to generate
When the first pressurizing member is located at the first position and when the first pressurizing member is located at the second position, between the first pressurizing member and the second pressurizing member and the opposing member. A pinching force is generated by the urging mechanism ,
The moving mechanism
A first urging member that urges the first pressurizing member from the first position toward the second position, and urges the first pressurizing member toward the second pressurizing member. The first urging member and
A cam provided on the first pressurizing member and moving the first pressurizing member from the second position toward the first position against the urging force of the first urging member is provided.
The first pressurizing member is a fixing device characterized in that the cam is located at the first position when the cam comes into contact with the second pressurizing member. The fixing device according to claim 1 , wherein the first pressurizing member is located at the second position by separating the cam from the second pressurizing member. The first pressurizing member can move in the moving direction with respect to the frame at a position upstream of the second pressurizing member in the moving direction.
The fixing device according to claim 1 or 2 , wherein the second pressurizing member has a fixed position with respect to the frame in a direction orthogonal to the width direction of the endless belt. The frame has an insertion hole through which the rotation shaft of the cam is inserted.
The fixing device according to claim 3 , wherein the length of the insertion hole in the moving direction is larger than the outer diameter of the rotation shaft of the cam. The second pressurizing member includes a pressurizing roller and a bearing that supports a rotation shaft of the pressurizing roller.
Wherein the first pressure member, the cam that abuts on the bearing fixing device according to any one of claims 1 to 4, characterized in that positioned in the first position. With a rotating endless belt,
Opposing members and
A first pressure member that comes into contact with the inner peripheral surface of the endless belt and sandwiches the endless belt with the opposing member.
A second pressure member that comes into contact with the inner peripheral surface of the endless belt and sandwiches the endless belt with the opposing member.
A frame that supports the first pressurizing member and the second pressurizing member, and
In the moving direction of the portion of the endless belt located between the first pressurizing member and the second pressurizing member, the first pressurizing member is placed at the first position and the first position. A moving mechanism that moves between different second positions,
By urging one of the frame and the opposing member toward the other, a holding force for sandwiching the endless belt between the first pressing member and the second pressing member and the opposing member. Equipped with an urging mechanism to generate
When the first pressurizing member is located at the first position and when the first pressurizing member is located at the second position, between the first pressurizing member and the second pressurizing member and the opposing member. A pinching force is generated by the urging mechanism ,
The moving mechanism
A first urging member that urges the first pressurizing member from the first position toward the second position, and urges the first pressurizing member toward the second pressurizing member. The first urging member and
A cam provided on the second pressurizing member and moving the first pressurizing member from the second position toward the first position against the urging force of the first urging member is provided.
The first pressurizing member is a fixing device characterized in that the cam is located at the first position when the cam comes into contact with the first pressurizing member. The fixing device according to claim 6 , wherein the first pressurizing member is located at the second position by separating the cam from the first pressurizing member. The first pressurizing member can move in the moving direction with respect to the frame at a position downstream of the second pressurizing member in the moving direction.
The fixing device according to claim 6 or 7 , wherein the second pressurizing member has a fixed position with respect to the frame in a direction orthogonal to the width direction of the endless belt. The first pressurizing member includes a pressurizing roller and a bearing that supports the rotating shaft of the pressurizing roller.
The frame has a fitting hole into which the bearing fits.
The fixing device according to claim 8 , wherein the length of the fitting hole in the moving direction is larger than the outer diameter of the bearing. The fixing device according to claim 9 , wherein the cam comes into contact with the bearing. The fixing device according to claim 5 , wherein the contact surface of the cam with the bearing has a recess for accommodating a part of the bearing.

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